A zirconia sintered body can be made to be a member having a high-grade appearance, since it has glossiness in addition to high toughness and high strength. Thus, a zirconia sintered body is utilized, for example, as various members such as luxury timepiece members or ornaments. Despite being a member having a high-grade appearance, the color tone of the zirconia sintered body is monochromatic. Further, usually, zirconias having different color tones are different from each other in their behaviors in sintering. Therefore, when zirconias having different color tones were simultaneously sintered, breakage, cracking, strain, etc. were likely to result, and it was impossible to obtain a defect-free zirconia sintered body. Thus, it was impossible to obtain a zirconia sintered body having two or more different color tones, or a member made thereof.
In order to obtain a member having two or more different color tones using a zirconia sintered body, a member was studied wherein a zirconia sintered body was combined with a material other than a zirconia sintered body, having a color tone different from the zirconia sintered body (e.g. Patent Documents 1 to 3). However, in such a member, textures of the materials were substantially different. Therefore, the obtained member exhibited design characteristics different from a member made solely of ceramics, and particularly was one impairing the high-grade appearance specific to a zirconia sintered body.
Further, a ceramics-bonded product was known wherein at least two ceramics were bonded via an interlayer. However, such a ceramics-bonded product was likely to undergo breakage starting from a point in the interlayer. Therefore, such a product bonded via an interlayer is not desirable for a zirconia sintered body which is characterized by high toughness and high strength.
On the other hand, in Patent Document 4, a zirconia sintered body obtained by sintering two zirconia green bodies different in color tone, is reported. Patent Document 4 discloses a zirconia sintered body obtained by sintering a green body of a zirconia powder containing FeCrNi spinel and a green body of a zirconia powder containing CoAl.